Influence of inorganic soil N, yield potential, and market class on irrigated spring wheat response to N

Abstract

Abstract Fertilizer N recommendations for small grains are frequently based on soil test N but data is limited for irrigated spring wheat. The relative grain yield response of irrigated spring wheat to N as affected by inorganic soil N (NO3‐N and NH4‐N), yield potential and market class was evaluated in thirteen Southern Idaho field experiments involving N rates. Experiments were conducted on silt loam soils from 1978 to 1986. Preplant soil NO3‐N and NH4‐N to a depth of 60 cm and ranging from 27 to 142 kg/ha accounted for approximately 73% of the relative yield variability. NO3‐N and NH4‐N were significantly correlated (r=.72). NH4‐N with NO3‐N did not account for more of the relative yield variability than using NO3‐N alone. Inorganic N in the first 30 cm and the second 30 cm were significantly correlated (r=.69) but N in the first depth increment accounted for more of the relative yield variability. The linear regression coefficient relating inorganic N in the first 30 cm to relative yield of unfertiliz...